This invention provides a process in which orientable thermoplastic film is converted simultaneously into an embossed oriented film. Moreover, by use of certain thermoplastic films in the process, novel thin embossed films having desirable strength properties are produced. Such films are useful in the manufacture of backsheets for diapers, surgical dressings, sanitary napkins, etc., and for various packaging applications.
In accordance with this invention there is provided a method of producing oriented or strength-enhanced embossed film which comprises (i) introducing into the nip between at least one pair of rotating compression rolls one or more thermoplastic films having an inert liquid lubricant covering the film surfaces proximate to at least one pair of said compression rolls, the pressure between at least said one pair of compression rolls being sufficient to reduce the thickness of the film(s) passing through the nip thereof; and (ii) simultaneously embossing at least one film surface within said nip.
Two or more films may be superimposed on each other and passed through the compression rolls in order to effect the reduction in film thickness, film orientation or strength enhancement, and film embossing. When applying the process to two or more superposed films, the two outer sides of the film bundle are thoroughly wetted with the lubricant, preferably by spraying the lubricant (e.g., water) thereon as the superposed films are proceeding into the compression nip. Thus the outer side of the outermost films directly confronting the rolls are wet as they are proceeding into the nip.